Weight stack assembly for exercise machine

ABSTRACT

A weight stack for an exercise machine includes a plurality of weights arranged in a vertical stack. Each of the weights has a body portion with substantially parallel upper and lower surfaces and includes at least one open-ended, forwardly facing recess in the lower surface. Each of the recesses has a height and a width, with an aspect ratio of height divided by width being between about 0.06 and 0.375.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/162,068, filed Jun. 16, 2011, the disclosure of which is herebyincorporated herein in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to exercise equipment, andrelates more particularly to resistance systems for exercise equipment.

BACKGROUND OF THE INVENTION

Exercise devices, and in particular weight training machines, typicallyinclude a mechanical member that the user moves along a prescribed pathfor exercise. Conventionally, movement of the mechanical member isresisted in some fashion to render the movement more difficult andthereby intensify the exercise. The most common means for providingresistance to movement of the mechanical member is a unit that connectsthe mechanical member with one or more weights such that the weights areraised in response to the movement of the mechanical member.

Often the weights of an exercise machine are provided in a stack; any orall of the weights (which are typically identical in weight) can besecured to a connecting rod that extends through the entire weight stackvia apertures in the weights. The connecting member is theninterconnected with the mechanical member, either directly orindirectly, via a one or more of belts, chains, cables, levers, or othermeans. Movement of the mechanical member by a user is resisted by theweight secured to the connecting rod.

In one commonly employed configuration, the weights are secured to theconnecting rod via a selecting pin, which can be inserted through anaperture included in each weight or a gap between weights and into anopening in the connecting rod. Insertion of the connecting pin into aconnecting rod aperture causes the portion of the weights in the stackabove the pin (i.e., those weights positioned between the pin and theinterconnecting belt) to travel as a substack with the connecting rodand thereby provide resistance to movement of the exercise arm; theportion of the weights in the stack below the pin (i.e., those weightspositioned farther from the interconnecting belt than the pin) remainstationary and provide no resistance to movement of the exercise arm. Ofcourse, the amount of weight providing resistance to the movement isequal to the weight of the substack of weights travelling with theconnecting rod. The amount of resistive weight can be easily adjusted byrepositioning the selecting pin in the connecting rod in a differentweight or between different weights so that a different number ofweights travel with the connecting rod.

Space limitations often restrict the number of weights that are includedin a weight stack. Because it is desirable to provide exercise machinesthat can be comfortably used by virtually any user (which may includeboth weak or infirm individuals using the machine for rehabilitation andvery strong individuals for whom substantial resistance is required),the weights typically provided are rather heavy. Also, generally theindividual weights in a stack are of the same magnitude. As the weightsin a stack are generally both heavy and uniform in magnitude, theincremental increase in resistance experienced by a user adding but asingle weight to the travelling substack can be quite significant. Suchan increase can be particularly onerous for novices, rehabilitationpatients, elderly users, and others who lack strength.

One attempt to address the problem of an overly high incremental weightincrease is offered in U.S. Pat. No. 4,834,365 to Jones. The Jonesmachine includes two weight stacks: one stack comprising conventionalheavier weights; and one stack comprising much lighter weights. Thesestacks are positioned so that the stack of lighter weights residesdirectly above the stack of heavier weights. Both stacks share a commonconnecting rod to which a portion of their weights can be secured. Whenthe mechanical member of the exercise machine is moved, the desirednumber of weights of both stacks travel with the connecting rod andprovide resistance. The lighter weights contribute to the resistanceexperienced by the user and therefore provide more resistance magnitudeoptions. For example, a rehabilitating patient may be exercising on amachine that has a large weight stack of twenty pound weights and alighter weight stack of one pound weights. If the patient'srehabilitation is best served by a resistance of thirty pounds, he canadd resistance in one pound increments with the lighter weight stack toa twenty pound weight from the heavier stack to total thirty poundsrather than being forced to proceed directly from twenty to forty poundsof resistance.

Another approach is discussed in U.S. Pat. No. 5,776,040 to Webb, whichincludes separate stacks of lighter (e.g., one-pound) and heavier (e.g.,ten-pound) weights, each with its own connecting rod and pin. The weightstacks are positioned side-by-side. Each connecting rod is attached toits own belt, with the belts following similar paths over pulleyassemblies that are coupled to a movement arm. By selecting weights fromboth weight stacks, the exerciser can select precisely an amount ofweight desired for resistance.

In view of the foregoing, it may be desirable to provide additionalweight systems that provide resistance in small increments.

SUMMARY OF THE INVENTION

As a first aspect, embodiments of the present invention are directed toa weight stack for an exercise machine. The weight stack comprises aplurality of weights arranged in a vertical stack. Each of the weightshas a body portion with substantially parallel upper and lower surfacesand includes at least one open-ended, forwardly facing recess in thelower surface. Each of the recesses has a height and a width, with anaspect ratio of height divided by width being between about 0.06 and0.25.

As a second aspect, embodiments of the present invention are directed toa weight stack assembly for an exercise machine, comprising: a pluralityof weights arranged in a vertical stack, each of the weights having abody portion with substantially parallel upper and lower surfaces andincluding at least one open-ended, forwardly facing recess in the lowersurface; a post extending through the plurality of weights, the postconfigured to connect with a movement arm of an exercise machine, thepost including a column of oblong apertures that align with the recessesof the weights; and a selector unit with upper and lower prongs, thelower prong configured to be inserted into one of the recesses and oneof the apertures of a first weight, and the upper prong configured to beinserted into one of the recesses and one of the apertures of a secondweight, the second weight being disposed above the first weight in theweight stack. Insertion of the prongs selects a portion of the weightsto provide resistance for exercise.

As a third aspect, embodiments of the present invention are directed toa weight for an exercise machine, comprising: a body portion withparallel upper and lower surfaces, opposed side edges, and opposed frontand rear edges; a pair of open-ended slots extending from the front edgeof the body portion; and an aperture located generally in the center ofthe body portion. The slots are connected with the aperture. The slotsare off-center relative to the side edges of the body portion.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a perspective view of a weight stack for an exercise machineaccording to embodiments of the present invention.

FIG. 2 is a front view of the weight stack of FIG. 1.

FIG. 2A is an enlarged perspective view of the area “A” of FIG. 4.

FIG. 3 is a partially exploded perspective view of the weight stack ofFIG. 1.

FIG. 4 is a perspective view of the selector fork employed with theweight stack of FIG. 1.

FIG. 5 is a side view of the weight stack of FIG. 1.

FIG. 6 is a bottom perspective view of a weight of the weight stack ofFIG. 1.

FIG. 7 is a partial perspective view of the center post, selector forkand two weights of the weight stack of FIG. 1.

FIG. 8 is a partial perspective view of a selector fork, center post andweight according to embodiments of the present invention.

FIG. 9 is a perspective view of a weight stack for an exercise machineaccording to other embodiments of the present invention.

FIG. 10 is a front view of the weight stack of FIG. 1.

FIG. 10A is an enlarged perspective view of the area “A” of FIG. 4.

FIG. 11 is a partially exploded perspective view of the weight stack ofFIG. 1.

FIG. 12 is a perspective view of the selector fork employed with theweight stack of FIG. 1.

FIG. 13 is a side view of the weight stack of FIG. 1.

FIG. 14 is a bottom perspective view of a weight of the weight stack ofFIG. 1.

FIG. 15 is a partial perspective view of the center post, selector forkand two weights of the weight stack of FIG. 1.

FIG. 16 is a partial perspective view of a selector fork, center postand weight according to embodiments of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The present invention will now be described more fully hereinafter, inwhich preferred embodiments of the invention are shown. This inventionmay, however, be embodied in different forms and should not be construedas limited to the embodiments set forth herein. Rather, theseembodiments are provided so that this disclosure will be thorough andcomplete, and will fully convey the scope of the invention to thoseskilled in the art. In the drawings, like numbers refer to like elementsthroughout. Thicknesses and dimensions of some components may beexaggerated for clarity.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof. As used herein the expression“and/or” includes any and all combinations of one or more of theassociated listed items.

Well-known functions or constructions may not be described in detail forbrevity and/or clarity.

Referring now to the drawings, a weight stack assembly for an exercisemachine, designated broadly at 10, is shown in FIGS. 1-7. The weightstack assembly 10 comprises a top weight 12 and a plurality of weights20 arranged in vertically stacked relationship. The top weight 12 has agenerally flat body 13. The top weight 12 is also attached to bushings18 that surround guide rods (not shown) that help to guide the weightstack 10 as some or all of the weights 20 are raised vertically duringexercise.

A center post 15 (best seen in FIG. 7) extends below the body 13 throughthe stacked weights 20, and also forms an attachment tab 14 that extendsabove the body 13 for attachment to a rope, cable or the like that isconnected, either directly or indirectly, to a movement arm of anexercise machine. The center post 15 includes oblong holes 16 that arearranged in aligned fashion (see FIG. 7). In some embodiments, the holes16 have an aspect ratio (height/width) of between about 0.06 and 0.25.

Each of the weights 20 is substantially identical to the other weights20. As such, only one weight 20 is described in detail herein, with theunderstanding that the discussion is equally applicable to the otherweights 20 also.

Referring now to FIG. 6, it can be seen that each of the weights 20includes a generally flat body portion 21. An open-ended, forwardly- anddownwardly-facing recess 22 extends from the front edge of the weight 20to a centrally-located, generally rectangular post aperture 26, whereinthe center post 15 is received, then further rearwardly from the postaperture 26. Each weight 20 also includes a pair of holes 24 that arealigned with the bushings 18 of the top weight to receive the guide rodsof the system.

In some embodiments, the weights 20 are relatively thin. In certainembodiments, the weights 20 are between about ¼ or ⅜ inch to ⅝ or ¾ inchin thickness; in some embodiments they may be as thick as ⅜ to ½ inch.In some embodiments, the weights 20 are five pound weights, although anymagnitude can be employed with the present invention. The recess 22typically has an aspect ratio (i.e., the ratio of the width of therecess 22 to the height of the recess 22) of between about 0.06 and0.375, which may be beneficial if the weights 22 are indeed thin.

As can be seen in FIGS. 1-3 and 5, the weights 20 are arranged invertically stacked fashion, with the recess 22 of each weight 20 beingpositioned to align with “column” of holes 16 of the center post 15(this is best seen in FIG. 2). Also, each weight 20 is of a thicknesssuch that, when arranged in a vertical stack as shown in FIGS. 1-3 and5, the weight 20 is level with one of the holes 16. As a result, each ofthe holes 16 can be accessed through one of the recess 22.

A selector fork 30 is shown in FIG. 4. The selector fork 30 includesupper and lower flattened prongs 32 a, 32 b that extend from a head 34.A pointer 36 extends from the head 34 on one side near the lower prong32 b. In some embodiments, the upper and lower prongs 32 a, 32 b have anaspect ratio of between about 0.06 and 0.25. As an example, the prongs32 a, 32 b may have a height of about 0.125 to 0.25 inch and a width ofabout 0.75 to 1.25 inches.

As shown in FIGS. 1-3 and 5, the selector fork 30 can be inserted intothe weights 20 by orienting the head 34 so that the prongs 32 a, 32 bare vertically aligned. In this orientation, the prongs 32 a, 32 b canbe received within respective recess 22 of two weights 20′, 20″ that areseparated by a third weight 20′″. Once in the recess 22, the prongs 32a, 32 b are inserted into the holes 16 of the center post 15 thatcorrespond to those particular slots 22. In this position, the lowerprong 32 b will underlie the weight 20″ immediately above it and supportit from underneath (see FIGS. 5 and 7).

In selecting a particular resistance for exercise, the exerciser shouldinsert the selector fork 30 so that the recess 22 of the lower weight20″ receives the lower prong 32 b represents the desired resistance. Forexample, in FIGS. 2 and 2A, the upper weight 20′ is designated “115”,the lower weight 20′ is designated “120”, and the middle weight 20″therebetween is designated “120”; the resistance that would be providedby such insertion would be the 125 pounds of the lower weight 20″. Ascan be seen in FIG. 2A, the pointers 36 is positioned to point to thelower weight 20″ upon insertion of the selector fork 30 into therecesses 22, thereby clearly indicating to the exerciser the magnitudeof the resistance.

As the exerciser manipulates a movement arm (and, in turn, raises thecenter post 15) during exercise, the magnitude of resistance isdetermined by the number of weights 20 selected via the selector fork 30to rise with the center post 15. As can be discerned from FIGS. 1-3 and5, the lower prong 32 b fits within the recess 22 of the lower weight20″ and immediately below the body portion 21 of the lower weight 20″.Because the lower prong 32 b supports the lower weight 20″ fromunderneath, raising of the center post 15 via movement of the movementarm lifts the lower weight 20″ and the weights 20 above it, therebyproviding resistance to the movement of the movement arm; the weights 20below the lower weight 20″ do not travel upwardly with the center post15.

The thin profile of the prongs 32 a, 32 b of the selector pin 30 canenable the use of thinner (and thus lighter) weights 20 than aretypically employed for weight stacks of this type. As a result, thedegree of resistance for exercise can be more precisely selected eventhough the weight stack may occupy the same volume as in prior machines.

FIG. 8 illustrates a differently configured selector fork 50. Theselector fork 50 includes a single prong 52 that extends from a head 54.A pointer 56 extends from the head 54. In selecting a particularresistance for exercise, the exerciser should insert the selector fork50 so that the weight 20 that receive the selector fork prong 52 withinits recess 22 represents the desired resistance. The pointer 56 pointsto that particular weight 20.

Another embodiment of a weight stack assembly for an exercise machine,designated broadly at 10, is shown in FIGS. 9-15. The weight stackassembly 110 comprises a top weight 112 and a plurality of weights 120arranged in vertically stacked relationship. Like the top weight 12described above, the top weight 112 has a generally flat body 113 and isalso attached to bushings 118 that surround guide rods (not shown) thathelp to guide the weight stack 110 as some or all of the weights 120 areraised vertically during exercise.

A center post 115 (best seen in FIG. 15) extends below the body 113through the stacked weights 20, and also forms an attachment tab 114that extends above the body 113 for attachment to a rope, cable or thelike that is connected, either directly or indirectly, to a movement armof an exercise machine. Unlike the center post 15, the center post 115includes two sets of open-ended oblong apertures 116 a, 116 b along itsside edges. In some embodiments, the apertures 16 have an aspect ratio(height/width) of between about 0.125 and 0.25.

Each of the weights 120 is substantially identical to the other weights120. As such, only one weight 120 is described in detail herein, withthe understanding that the discussion is equally applicable to the otherweights 120 also.

Referring now to FIG. 14, it can be seen that each of the weights 120includes a generally flat body portion 121. Two open-ended, forwardly-and downwardly-facing recesses 122 a, 122 b extend from the front edgeof the weight 120 to a centrally-located, generally rectangular postaperture 126, wherein the center post 115 is received, then furtherrearwardly from the post aperture 126. The recesses 122 a, 122 b areoffset from the center of the body portion 121 toward the side edgesthereof. Each weight 20 also includes a pair of holes 124 that arealigned with the bushings 118 of the top weight to receive the guiderods of the system.

In some embodiments, the weights 120 are relatively thin. In certainembodiments, the weights 120 are between about ¼ or ⅜ inch to ⅝ or ¾inch in thickness; in some embodiments they may be as thick as ⅜ to ½inch. In some embodiments, the weights 120 are five pound weights,although any magnitude can be employed with the present invention. Therecesses 122 a, 122 b typically have an aspect ratio (i.e., the ratio ofthe width of the recess 122 a, 122 b to the height of the recess 122 a,122 b) of between about 0.06 and 0.375, which may be beneficial if theweights 120 are indeed thin.

As can be seen in FIGS. 9-11 and 13, the weights 120 are arranged invertically stacked fashion, with the recesses 122 a, 122 b of eachweight 120 being positioned to align with the “columns” of apertures 116a, 116 b of the center post 115 (this is best seen in FIG. 10). Also,each weight 120 is of a thickness such that, when arranged in a verticalstack as shown in FIGS. 9-11 and 13, the weight 120 is level with onepair of the apertures 116 a, 116 b. As a result, each of the apertures116 a, 116 b can be accessed through one of the recesses 122 a, 122 b.

A selector fork 130 is shown in FIG. 11. The selector fork 30 includestwo flattened upper prongs 132 a, 132 b and two flattened lower prongs133 a, 133 b that extend from a head 134. A pointer 136 extends from thehead 134 on one side near the lower prong 133 b. In some embodiments,the upper and lower prongs 132 a, 132 b, 133 a, 133 b have an aspectratio of between about 0.125 and 0.25. For example, the prongs 32 a, 32b, 33 a, 33 b may have a height of between about 0.125 to 0.25 inch anda width of between about 0.5 to I inch.

As shown in FIGS. 9-11 and 13, the selector fork 130 can be insertedinto the weights 120 by orienting the head 34 so that the upper prongs132 a, 132 b are vertically aligned with the lower prongs 133 a, 133 b.In this orientation, the upper prongs 132 a, 132 b can be receivedwithin respective recesses 122 a, 122 b of a first weights 120′, and thelower prongs 133 a, 133 b can be received within respective recesses 122a, 122 b of a second weight 120″. The first and second weights 120′,120″ are separated by a third weight 120′″. Once in the recessess 122 a,122 b, the prongs 132 a, 132 b, 133 a, 133 b are inserted into theapertures 116 a, 116 b of the center post 115 that correspond to thoseparticular recesses 122 a, 122 b. In this position, the lower prongs 133a, 133 b will underlie the weight 120″ immediately above them andsupport the weight 120″ from underneath.

In selecting a particular resistance for exercise, the exerciser shouldinsert the selector fork 30 so that the lower weight 120″ receives thelower prongs 133 a, 133 b represents the desired resistance. Forexample, in FIG. 10A, the upper weight 120′ is designated “115”, thelower weight 120″ is designated “125”, and the middle weight 120′″therebetween is designated “120”; the resistance that would be providedby such insertion would be the 125 pounds of the lower weight 120″. Ascan be seen in FIG. 10A, the pointer 136 is positioned to point to thelower weight 120″ upon insertion of the selector fork 130 into therecesses 122 a, 122 b of the lower weight 120″, thereby clearlyindicating to the exerciser the magnitude of the resistance.

As with the weight stack 10, as the exerciser manipulates a movement arm(and, in turn, raises the center post 115) during exercise, themagnitude of resistance is determined by the number of weights 120selected via the selector fork 130 to rise with the center post 115. Ascan be discerned from FIG. 8, the lower prongs 133 a, 133 b fit withinthe recesses 122 a, 122 b of the lower weight 120″ and immediately belowthe body portion 121 of the lower weight 120″. Because the lower prongs133 a, 133 b support the lower weight 120″ from underneath, raising ofthe center post 115 via movement of the movement arm lifts the lowerweight 120″ and the weights 120 above it, thereby providing resistanceto the movement of the movement arm; the weights 120 below the lowerweight 120″ do not travel upwardly with the center post 115.

As was the case with the lower prong 32 b discussed above, the thinprofile of the prongs 133 a, 133 b of the selector pin 130 can enablethe use of thinner (and thus lighter) weights 120 than are typicallyemployed for weight stacks of this type. As a result, the degree ofresistance for exercise can be more precisely selected even though theweight stack may occupy the same volume as in prior machines.

FIG. 16 illustrates the weight stack 110 utilizing a differentlyconfigured selector fork 150. The selector fork 150 includes two prongs152 a, 152 b that extend from a head 154. A pointer 156 extends from thehead 54. In selecting a particular resistance for exercise, theexerciser should insert the selector fork 150 so that the weight 120that receives the selector fork prongs 152 a, 152 b within its recesses122 a, 122 b represents the desired resistance. The pointer 56 points tothat particular weight 120. The prongs 152 a, 152 b are received in thecorresponding apertures 116 a, 116 b of the center post 115.

Those skilled in this art will recognize that, although the weights 20,120 are illustrated as being 5 pound weights, weights of a differentmagnitude (e.g., 10 pound weights) may also be used. Also, the weights20, 120 are shown as being generally rectangular in shape, but may takeother shapes (e.g., circular, oval, or triangular) as desired.

Other variations from the illustrated embodiments are also contemplated.For example the center posts 15, 115 may take a differentcross-sectional shape, or in some embodiments two separate, parallelcenter posts may be employed. Also, selector units other than theselector pin and selector forks may be employed. Further deviations fromthat illustrated and explicitly described may also be employed.

It should also be noted that the weight stack assemblies 10, 110 may beemployed with a variety of exercise machine types. For example, theweight stack assemblies 10, 110 may be employed with: machines for legexercise, such as leg curl, leg press, and calf machines; machines forhip exercise, such as hip abduction, adduction, and abduction/adductionmachines, machines for neck exercise, such as 4-way neck, behind neck,and neck and shoulders machines; machines for the upper torso, such as10-degree and 50-degree chest, chest and double chest, declined andinclined press, bench press, reverse and super pullover, torso arm,seated dip, rowing back, and compound row machines; machines for themid-torso, such as abdominal, lower abdominal, rotary torso, and lowback machines; machines for the arms, such as multi-biceps,multi-triceps, and super forearm machines; and machines for theshoulders, such as lateral raise, overhead press, and rotary shouldermachines.

The foregoing is illustrative of the present invention and is not to beconstrued as limiting thereof. Although exemplary embodiments of thisinvention have been described, those skilled in the art will readilyappreciate that many modifications are possible in the exemplaryembodiments without materially departing from the novel teachings andadvantages of this invention. Accordingly, all such modifications areintended to be included within the scope of this invention as defined inthe claims. The invention is defined by the following claims, withequivalents of the claims to be included therein.

That which is claimed is:
 1. A weight stack for an exercise machine,comprising: a plurality of weights arranged in a vertical stack, each ofthe weights having a body portion with substantially parallel upper andlower surfaces and including two open-ended, forwardly facing recessesin the lower surface, each of the recesses having a height and a width,and wherein an aspect ratio of height divided by width is between 0.06and 0.375.
 2. The weight stack defined in claim 1, wherein each of theweights includes an aperture connected with its recesses, the apertureconfigured to receive a center post.
 3. The weight stack defined inclaim 2, wherein the recesses extend rearwardly beyond the aperture. 4.The weight stack defined in claim 3, wherein the aperture of each weightis located generally in the center of the weight.
 5. The weight stackdefined in claim 1, wherein the weights are between about ¼ and ¾ inchin thickness.
 6. A weight stack assembly for an exercise machine,comprising: a plurality of weights arranged in a vertical stack, each ofthe weights having a body portion with substantially parallel upper andlower surfaces and including at least one open-ended, forwardly facingrecess in the lower surface; a post extending through the plurality ofweights, the post configured to connect with a movement arm of anexercise machine, the post including a column of oblong apertures thatalign with the recesses of the weights; and a selector unit with upperand lower prongs, the lower prong configured to be inserted into one ofthe recesses and one of the apertures of a first weight, and the upperprong configured to be inserted into one of the recesses and one of theapertures of a second weight, the second weight being disposed above andadjacent the first weight in the weight stack, insertion of both of theprongs selecting a portion of the weights to provide resistance forexercise.
 7. The weight stack assembly defined in claim 6, wherein theselector unit includes a single upper prong and a single lower prong. 8.The weight stack assembly defined in claim 7, wherein the selector unitfurther comprises an indicator that designates the weight immediatelyabove the lower prong.
 9. The weight stack assembly defined in claim 7,wherein the at least one recess is generally centered between side edgesof the weight.
 10. The weight stack assembly defined in claim 6, whereinthe at least one recess of each weight is two recesses, and wherein theselector unit includes a pair of upper prongs and a pair of lowerprongs.
 11. The weight stack assembly defined in claim 9, wherein theselector unit further comprises an indicator that designates the weightimmediately above the lower prong.
 12. The weight stack assembly definedin claim 10, wherein each of the recesses is slightly offset from centerbetween side edges of the weight.
 13. The weight stack assembly definedin claim 6, wherein the apertures of the center post are closed-endedapertures.
 14. The weight stack assembly defined in claim 6, wherein theapertures of the center post are open ended apertures located on theside edges of the center post.
 15. The weight stack assembly defined inclaim 6, wherein the weights are between about ¼ and ¾ inch inthickness.
 16. A weight for an exercise machine, comprising: a bodyportion with parallel upper and lower surfaces, opposed side edges, andopposed front and rear edges; a pair of open-ended recesses extendingfrom the front edge of the lower surface of the body portion; and anaperture located generally in the center of the body portion; whereinthe recesses are connected with the aperture; and wherein the recessesare off-center relative to the side edges of the body portion.
 17. Theweight defined in claim 16, wherein the aperture is generallyrectangular.
 18. The weight defined in claim 16 having a thickness ofbetween about ¼ and ¾ inch.
 19. The weight stack defined in claim 1,wherein the weights are between ¼ and ⅝ inch in thickness.